• Bulletin of the Korean Chemical Society
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• v.34 no.6
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• pp.1679-1683
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• 2013

Intergrowth perovskite type complex oxides $La_{0.8}Ln_{0.2}Sr_2MnCrO_{7-{\delta}}$ (Ln=La, Nd, Gd, and Dy) have been synthesized by sol-gel method. Rietveld profile analysis shows that the phases crystallize with tetragonal unit cell in the space group I4/mmm. The unit cell parameters a and c decrease with decreasing effective ionic radius of the lanthanide ion. The magnetic studies suggest that the ferromagnetic interactions are dominant due to $Mn^{3+}$-O-$Mn^{4+}$ and $Mn^{3+}$-O-$Cr^{3+}$ double exchange interactions. Both Weiss constant (${\theta}$) and Curie temperature ($T_C$) increase with decreasing ionic radius of lanthanide ion. It was found that the transport mechanism is dominated by Mott's variable range hopping (VRH) model with an increase of Mott localization energy.

• Journal of the Korean Vacuum Society
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• v.12 no.S1
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• pp.67-69
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• 2003

The magnetic properties of single- and poly-crystalline $La_{0.7}Sr_{0.3}MnO_3/Pr_{0.65}Ca_{0.35}MnO_3$ multilayered (ML) films, and composite (CP) $(La_{0.7}Sr_{0.3})_{0.5}(Pr_{0.65}Ca_{0.35}_{0.5}MnO_3$ films, prepared by laser ablation, have been investigated in a wide temperature range. It was shown that the transformation from an incoherent to a coherent interface in the ML films leads to an enhancement of the ferromagnetic coupling between layers and to a single-phase magnetic transition. The amorphous CP films demonstrate a paramagnetic behavior of the magnetization with a sharp peak at $T_{G}\approx$45 K, which was interpreted as the formation of Griffiths phase. A short-term annealing at $750^{\circ}C$ induced the complete crystallization of film, and a recovery of the ferromagnetic and the metal-insulator transitions.

• Proceedings of the Korean Magnestics Society Conference
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• 2002.12a
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• pp.102-103
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• 2002

LaMnO$_3$에 Ca을 치환한 Mn계 perovskite 구조(ABO3)의 물질에서 초거대자기저항 현상이 발견된 이후 R$_{1-x}$$^{3+}$ A$_{x}$$^{2+}$MnO$_3$(R=La, Nd, Pr: 희토류금속, A=Ca, Sr, Ba, Cd, Pb; 2가 양이온)계의 Mn 산화물의 연구가 고감도 자기 저항 센서와 자기기록 등의 활용가능성을 중심으로 활발히 진행되고 있다. 자기적 특성이 뛰어난 초거대자기저항물질에 대한 미시적인 자성에 대한 연구는 그 메커니즘이 복잡하고 다양한 접근방식에 따른다. (중략)

• Journal of the Korean Magnetics Society
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• v.10 no.4
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• pp.149-153
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• 2000

Large magnetic entropy change in single crystalline and polycrystalline perovskite manganites La$_{0.7}$Ca$_{0.3}$MnO$_3$ has been observed as magnetic field is changed. The large magnetic entropy change is believed to be caused by the abrupt reduction in magnetization as a result of 1st order-like magnetic transition. The large magnetic entropy change and easiness of the Curie temperature manipulation in the temperature range 100 K

• Journal of the Korean Ceramic Society
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• v.38 no.1
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• pp.84-92
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• 2001

(La,Sr)MnO$_3$(LSM)-YSZ 복합체 양극의 산소환원 반응기구에 대해 고찰하였다. YSZ를 첨가함에 따라 복합체 양극의 ohmic 저항이 증가하고, 분극 저항은 YSZ를 40 wt%~50 wt% 혼합하였을 때 최소값을 나타내었다. 또한 LSM-YSZ 복합체 양극의 산소환원 반응기구는 1가 산소이온의 표면확산과 산소이온전달반응에 의해서 지배됨을 알 수 있었다. 임피던스 분석 결과에 따르면 고주파수 영역에서 나타나는 반원은 산소이온전달반응으로 산소분압 의존성이 거의 없고, YSZ가 40 wt% 첨가되었을 때 최소값을 나타내었다. 중간주파수 영역에서 나타나는 반원은 1가 산소이온의 표면확산반응으로 산소분압 의존성은 약 1/4이고, YSZ가 40~50 wt% 첨가되었을 때 최소값을 나타냈다. 한편, 저주파수 영역에 나타나는 반원은 가스확산반응으로 산소분압 의존성이 1이고, 온도에 따른 의존성이 거의 없었다.

• Journal of the Korean Ceramic Society
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• v.35 no.8
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• pp.885-889
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• 1998

The temperature dependence of dc conductivity and magnetic properties of cation deficient {{{{ { {(LaMn) }_{1-λ }O }_{3 } }} systems has been investigated,. Above 160K the magnetic susceptibility of all samples followed the Curie-Weiss law. The Curie temperature decreased as the cation deficiency increased. This is due to a strong Jahn-Teller effect originated from electrons of {{{{ { Mn}^{3+ } }} In the case of samples annealed in air and oxygen at-mosphere the charge carriers responsible for conduction in the ferromagnetic regime below the Curie tem-perature are believed to have both magnetic and lattice characteristics. However the conduction carriers in the paramagnetic regime above the Curie temperature are though to be formed by hopping process of small polarons which were generated by assistance of the Jahn-Teller effect.

• Journal of the Korean Chemical Society
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• v.55 no.4
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• pp.697-702
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• 2011

The new layered perovskite manganites $La_{0.5}Sr_{1.5}Mn_{0.5}Cr_{0.5-x}Fe_xO_4$ (x=0.15, 0.3) have been prepared by standard ceramic method. The powder X-ray diffraction studies show that the phases crystallize with tetragonal unit cell in the space group I4/mmm. The electrical transport properties suggest that the phases show insulating behaviour and the electrical conduction in the phases occurs by a 3D variable range hopping mechanism. The magnetic properties suggest that both the phases are antiferromagnetic.

• Proceedings of the Korean Magnestics Society Conference
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• 2007.05a
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• pp.28.1-28.1
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• 2007

• Proceedings of the Korean Magnestics Society Conference
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• 1999.04a
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• pp.138-139
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• 1999

• Proceedings of the Korean Ceranic Society Conference
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• 2000.04a
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• pp.112.2-112.2
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• 2000